LC Fresnel lenses have a variety of applications, for example, in optical information processing, long-distance optical communications, optical interconnections, beam shaping devices, 3D display systems, etc. Conventional LC Fresnel lenses are typically made of nematic LCs, and have switching times greater than several milliseconds (and in some cases, even greater than 100 milliseconds).
One class of LC Fresnel lenses involves phase separation of a mixture of a liquid crystal and another material, typically polymer or dye, which exploits the refractive index difference between the background matrix and the additive.
Another class of LC Fresnel lenses employs patterned electrodes to generate a periodic electric field distribution to control the LC directors locally.
Yet another class of LC Fresnel lenses utilizes initially-guided LC directors to realize a periodic refractive index distribution (e.g., via a patterned polymer relief and UV-modified alignment films). This approach includes two different alignment domains to provide an alignment structure using Fresnel zones. These two different alignment domains may be a combination of planar and homeotropic alignment domains, a combination of planar and twist alignment domains, a combination of two planar alignment domains, etc.
These existing LC Fresnel lens architectures are characterized by low efficiency, complicated fabrication procedures, high driving voltage requirements (e.g., greater than 100 volts), and long switching times (e.g., on the order of hundreds of milliseconds). Such long switching times are unsuitable for many modern applications, which demand lenses having a very short response times (e.g., less than 1 millisecond).